Mears is demanding its workers are clean shaven so dust masks are fully effective.

The only exceptions are if a worker can’t shave for medical reasons, a dust mask can’t be worn for medical reasons or a person has a beard for religious reasons.

Unite regional official for London Mark Soave said: “The arrogance of Mears is hair-raising.

“This is a highly delicate issue, which has huge cultural, religious and personal issues and where sensitivity should be the watchword. Instead members have been handed a decree from on high.”

Mark Elkington, Group Health and Safety Director of Mears Group said: “We are pretty surprised that Unite, who claim to have the safety of workers at heart have taken this disappointing stance.

“Every employer in the UK has a legal responsibility to ensure that employees working in dusty or otherwise potentially hazardous environments are properly protected and in recent years employers have been prosecuted for failing to fulfil this duty.

“The simple fact is that no dust mask can work effectively unless it forms a seal against the skin.

“That is not possible with a beard or even heavy stubble. If the Health and Safety Executive did a spot site visit and found workers wearing dust masks that were not sealed against the face then we would be liable to prosecution.

“The alternative to a dust mask is a full hood over the head, which brings its own risks.

“For example many of our operatives do not like wearing a full hood and it can affect hearing and line of sight.

“It can also be uncomfortable to wear and can raise concerns with our clients who do not like to see workers in such hoods because of how it looks to customers.

“It is vital to note, however, that if a risk assessment shows that the hood is a better option for a job or a worker insisted on having one, then, if assessed to be suitable, we will supply that hood.

“If one of our workers suffers respiratory illness as a result of a poor fitting mask then that is our responsibility and we place the safety of our workers at the top of the priority list.

“Finally it is worthy of note that this affects a very small percentage of our workers who would be in that environment.

“One has to question the real motives of Unite which has chosen not to take the safety of its members seriously in order to make a cheap point.”

Matthew Judson, technical director at safety equipment specialist JSP said: “Mears cannot allow their staff to work if not properly protected.

“A mask cannot be tightfitting on stubble, there really is no argument on that. If you want protecting you need to shave or use the powered devices.”